Field of the Invention
The present invention describes pigment dispersions of a predetermined particle size employed for offset lithographic, flexographic, gravure and screen printing applications. The present invention also describes novel ink compositions including pigment dispersions.
Description of the Related Art
Pigments have been used by civilizations for thousands of years as a tool for expression. In ancient times, pigments were cast onto walls or murals to depict epic stories that were passed down from one generation to the next. In modern times, pigments have been used in various applications such as, for example, primary or secondary packaging, graphic arts, waterborne paints, cosmetics, pharmaceutical preparations, automotive coatings, industrial coatings.
Pigments are generally employed in combination with a binder/vehicle and intimately admixed into a carrier/solvent to ensure a stable dispersion. Stable dispersions require complete wetting of the pigments and their even distribution in the surrounding vehicle. Namely, these stable dispersions are colloidal suspensions which do not settle under their own gravitational forces. By so doing, the dispersed particles avoid reagglomeration and flocculation during further processing or storage.
To ensure maximum color strength, a narrow distribution of small sized pigment particles is preferred in a dispersion. Specifically, color strength is proportional to the exposed surface area of the pigment. Other characteristics such as gloss and transparency also are improved. With ever-increasing demands from consumers for end-products exhibiting improved color strength, gloss and transparency, a need thus exists in the market for pigment dispersions with small pigment particle sizes without compromising on stability. A further need exists in the art for employing such pigment dispersions and end-products, such as ink, coatings, or paints, in contact printing applications such as offset lithography, flexography, gravure printing and screen printing.
From a manufacturing perspective, pigments are the most expensive component of the pigment dispersion. With rising production costs and reduced profit margins in the manufacturing industry, cost-cutting measures have become a top priority for most pigment dispersion and ink manufacturers. A need thus exists for a pigment dispersion employing reduced pigment amounts while maintaining equal or improved color strength, gloss and transparency characteristics. A further need yet exists in the art for employing reduced pigment amounts in pigment dispersions and inks employed in contact printing applications such as offset lithography, flexography, gravure, and screen printing applications, different from non-contact printing applications such as ink jet printing.